Tube Mic RFI making me crazy!

[Ryan Silva]

Ever since I got the Red Type A tube condenser body I have had a huge problem with what I believe is RFI.

Sent it in to David O. Brown at Audio Technical Services in LA and he couldn?t find anything wrong with it. I later came to find out that it only happened in certain locations at my place. Used it for two 8 hour sessions at a residential house I was recording in, and it was also fine there.

Tube good
Wiring Good
Power Supply Good
Cable Good
Happens with all three of my Capsules

If it is in fact Radio Freq. Interference, what can I do?

Will linear filtering the AC solve the problem or will it just lessen it?

Need some help here!!!

Thanks

[digitaldrummer]

make sure the body of the mic is tight and that the edges make a good electrical connection - the metal body in many cases acts as a shield for the transformer (I know on my AA CM47 the transformer is not in its own metal shield). that may not be the problem, but something to check.

Mike

[Nick Sevilla]

Ever since I got the Red Type A tube condenser body I have had a huge problem with what I believe is RFI.

Sent it in to David O. Brown at Audio Technical Services in LA and he couldn?t find anything wrong with it. I later came to find out that it only happened in certain locations at my place. Used it for two 8 hour sessions at a residential house I was recording in, and it was also fine there.

Tube good
Wiring Good
Power Supply Good
Cable Good
Happens with all three of my Capsules

If it is in fact Radio Freq. Interference, what can I do?
Will linear filtering the AC solve the problem or will it just lessen it?
Need some help here!!!

Thanks

Hi Ryan,

The item in red should give you an indication that it most likely is not the microphone.

In those particular places in your place, which electrical circuit was used to power the mic? Are there any other special devices sich as A/C or other large electrical appliance connected to that circuit?

As a hint, I once had to call in the electrical company, since there was a faulty transformer outside my studio, which allowed the neighbor's large electrical compressor and arc welder's noise to come through to my building. So it may not be something too obvious, nor even something in the room itself.

Cheers

[Ryan Silva]

Thanks Nick,

After I got it back from the repair shop, I figured my mic was ok as well. Like I said, I had one outlet (circut) that gives me zero problems, but instead of running an AC cable around my place, would a Furman Line Filter help this? Isnt that what they are designed for?

Thanks

[rockstudio]

Just a thought, make sure you don't have phantom power on. I know some tube mics will sizzle and snap when the power is on, and you may be confusing that with RFI.

[Ryan Silva]

Just a thought, make sure you don't have phantom power on. I know some tube mics will sizzle and snap when the power is on, and you may be confusing that with RFI.

Funny you should mention that, I hadnt had the 48v engaged, but I did try to turn it on just for the heck of it, and it removed the hash sound for a short time 5 min maybe.

What's that all about?

[Nick Sevilla]

Thanks Nick,

After I got it back from the repair shop, I figured my mic was ok as well. Like I said, I had one outlet (circut) that gives me zero problems, but instead of running an AC cable around my place, would a Furman Line Filter help this? Isnt that what they are designed for?

Thanks

Hi Ryan,

It might. What frequencies is the noise?

[Producer/Engineer]

http://www.furmansound.com/product.php?div=01&id=M-8x2

http://www.sweetwater.com/store/detail/M8x2/

[Ryan Silva]

I really can't imagine why you would not plug anything into a Furman with EMI/RFI filtering. If your still getting "noise" after that, I would replace the tube in the mic. When tubes start to get microphonic, the "noise" can "come and go," which may lead you to believe that it's the "location."

It's like this: I had David O. Brown at Audio Technical Services, change out the Tube and he said both tubes were fine. What I didnt want to do was spend $500 dollars to 'slightly' fix a problem. Maybe masking the real issue, I would much prefer to track down the root cause. If I cant do that by tomorrow afternoon, I will be forced to spend the money and pick up a filtering device.

Thanks guys,

[Jim Williams]

Digi-Key and Mouser sell snap on ferrite rf clamps that snap over the mic cable for about a dollar each. Get some, snap them over the mic cables and that just might do the trick.

[ott0bot]

Digi-Key and Mouser sell snap on ferrite rf clamps that snap over the mic cable for about a dollar each. Get some, snap them over the mic cables and that just might do the trick.

thanks for thr suggestion. I'm having a similar issue with my Sputnik, and all the troubleshooting wasn't finding any real issues.

going to give them a try.

[fuzz]

I own a RED Type A and did have some noise in the beginning But it was due to the shield not getting a good connection in the cable. I've never had any rf problems with mic (being in the middle of Brooklyn) and it may help that my studio is star grounded.

Years ago when we had problems with amps virtually acting like boom boxes at a space in Kansas City, we would take a shielded copper wire and tape an end to a part of the chassis and the other to a water main that went deep into the ground. This is hardly practical but if Jim Williams recommendation doesn't fly I would look into improving your electrical source. And if the problem continues in very specific rooms then I'd try hanging metal plates on the offending wall. I've heard of some studios having to sheild themselves from RF this way.